The decision of United manager Sir Alex Ferguson to leave Rooney out of his starting line-up to face Real Madrid in the Champions League on Tuesday has sparked intense speculation that the 27-year-old could leave Old Trafford.

McClaren was a member of Sven-Goran Eriksson’s England backroom staff when Rooney shone at Euro 2004 before later succeeding the Swede as national boss. He also worked as Ferguson’s assistant from 1999 to 2001, and believes too much has been made of Rooney’s omission.

He said: 'Wayne Rooney is the first on the field and last off it. He works like a Trojan every day. He is a true professional. He is going to be a big player for Manchester United.'

Despite that, McClaren acknowledges that Ferguson will not hesitate to move a player on should he deem it necessary.

He said: 'That is one thing you can’t predict because you have seen such big players for Manchester United come and go in previous years.

'He will make that decision early. He plans. That is the difference between top managers and just below. They plan ahead. They are a helicopter, way above everybody, planning not just the next game but the next five games, the season, even next season.

'Trojan': McClaren said he was always impressed by Rooney's work rate during his time as England manager

'He plans ahead and will be planning ahead now. He plans everything for the good of Manchester United, not for the good of Wayne Rooney, (Robin) van Persie or any one player.

'Sir Alex will look every week, every day, every season at each individual player very closely in training and games and say what kind of condition they are in and is he still mentally right for Manchester United.

'If not, he will have no hesitation in removing a player. But for the moment, I cannot see his (Rooney’s) future beyond Manchester United.'